Method of flameproofing fibers and composition used therein



METHOD OF FLAMEPROOFING FIBERS AND COMPOSITION USED THEREIN James R. Costello, In, Chicago Heights, and Thornton P. Traise, South Chicago Heights, 11]., assignors to Victor Chemical Works, a corporation of Illinois Application September 22, 1953 Serial No. 381,762

8 Claims. (Cl. 117-136) No Drawing.

This invention relates to fiber treating compositions, methods of preparing said compositions and methods of flameproofing fabric.

The process is accomplished by treating the fabric with a polymer or partially brominated polymer of a di beta, gamma alkenyl beta-cyanoethanephosphonate and thereafter curing the impregnated material ata moderate temperature.

Suitable starting compounds for main the new flameproofing process are diallyl and dimethallyl esters of betacyanoethanephosphonate. The preparation of these monomeric starting compounds is described in the copending application of A. D. F. Toy and R. S. Cooper, Serial No. 381,765, filed September 22, 1953. Such esters are prepared by reacting a dialkenyl phosphite with acrylonitrile in the presence of a sodium alkenolate cata lyst under suitable reaction conditions. ,The reaction involved in the preparation of the monomeric dialkenyl beta, cyanoethanephosphonate may be illustrated by the equation:

The recovered ester compound may 'be employed with or without further purification in the present flameproofing process. Generally, it is preferred to use the distilled ester. a p

In the practice of the present invention the di beta, gamma alkenyl beta-cyanoethanephosphonate is dissolved in an equal weight of a solvent, such as Chlorex" (B,B' dichloroethyl ether), mixed with a small amount of a polymerization catalyst such as benzoyl peroxide and slowly heated until the viscosity of the solution has increased to about 2 to 4 times its original value. This change in viscosity is indicative of the degree of polymerization. With a viscosity change of four times, the degree of conversion to the partial polymer is of the order of 30 to 40%. The solution is then cooled and the partial polymer separated for use in the preparation of the fabric treating solution. I

The separation of the partial polymer is eifected by adding to the above solution a selective solvent such as ethyl ether, ethyl acetate or mixtures of ethyl acetate and hexane, and the like in which the partial polymer is substantially insoluble. The partial polymer is then separatedby filtration or decantation and "washed with additional quantities of -a selective solvent! The separated partial polymer is generally in'th'e form of a hard solid or gummy "mass depending on the amount of occluded monomer and the selective solvent employed. It is' 2,841,507 Patented July ,1, 1953 preferred that all monomeric ester be removed from the partial polymer before using the latter in the impregnating solution, though satisfactoy flameproofing may be effected using the crude gummy partial polymer.

The partial polymer prepared in the above manner is then dissolved in a suitable volatile solvent to form the fabric impregnating bath. We prefer to use a mixture of 30 parts methanol or ethanol and parts of ethylene dichloride, by volume, as the solvent, with the concentration of the partial polymer in the solvent being about 25% to 50%. The fabric is treated with this solution for a few minutes to allow good penetration following which the fabric is wrung out and cured by heating at approximately l00 C. for about 30 minutes. The resulting fabric has excellent flame resistant qualities which are not destroyed by subsequent washing in ordinary soap solutions.

The flameproofing character of the treated fabric is customarily tested according to themethod described as the Vertical Flame Resistance Test in the Supplement to Federal Specifications for Textiles; General Specifications Test Method CCC-T-19la or B (Method No. .5902); In this method a 2 /2 inch by 10 inch strip of the treated cloth is suspended vertically and ignited at the bottom with a Bunsen burner. Flame resistance ismeasured by the burning time of the cloth, total char, length of the burn, and amount of afterglow. A flameproofing process is generally held to be satisfactory if the burning time is less than 12 seconds, char length less than 9.inches and afterglow negligible. In addition to the above testsan indication of the value of the flameproofing process,

particularly with reference to the fiameproofing of clothing, is the character of the remaining char. A coherent, porous, reasonably flexible char is highly desirable because of its insulation qualities. Fabrics treated according to the methods of thisinvention easily meet the above:

specifications.

In typical examples according to our new flameproofing.

process a diallyl =beta-cyanoethanephosphonate ester was dissolved in an equal weight of Chlore'x (B,B' dichloroethyl ether) in a three necked flask equipped with stirrer, thermometer, nitrogen inlet and pipette with bulb at-.

tached. The temperature was raised to C. .with

stirring under a nitrogenatmosphere. Benzoyl peroxide was added to catalyze the polymerization. Polymerization was permitted to proceed until the change in viscosity was such that the discharge time through a 5 ml. pipette test purposes a strip of standard muslin or army twillj cloth 20" by 2 /2" in size was dipped into the above solution for 5 minutes, wrung out, dried and cured in an oven at l00108 C. The test strip of cloth was cut in half and one-half washed in 200 ml. water containing 0.5. gram soap at a temperature of .F. Both the washed.

and unwashed test strips were subjected to the standard flame test previously described. The data relating to the process and the flame test results are given in the following table.

emulsion procedure, as in the above example, to improve the stability of the emulsion and facilitate the impregna- Experiment No 257 258 261 262 336 206 212 Diallyl-cyanoethanephosphonate. 50 g 50 g 50 g 300 g 50 g 50 g. Chtlgrgx (B,B dichloroethyl 50 g 50 g 50 g 300 g 50 g 50 g.

e er Benzoyl peroxide catalyst 1 5 g 1.6 g 1.0 .25 g 9 1.25 g. Time of polymerization 38 mm 1 hr., mm.. 1 hr., 33 min.. 1 hr., 47 min 40 min Change in viscosity (times) 4.2. 4.0 4.05 4. 4.0. Isolation solvent (Acetone-.100 (Ethyl ace- Hexane (1,450 Ethylacetate Ethyl acetate, Ethyl ether.

ml.) (Hextate, 6,500 rnl. Eth (400 ml.) Hexane. ans 2. 1. 1111. aclet)ate 40o Hleane (20o m. m Conversion to polymer 32% 34.2% 30.8% 34.4% 37% 41.4%. Character of separated polymer. Solid Solid Solid Solid Solid Gummy mass- Solid. Impregnating soln: (30/70 methanol/ethylene chloride). Concentration (g./ml.). 0.2348 0.2493 0.2324 0.25 approx... 0.1627 0.25 approx.... 0.32. Add-0n to muslin cloth. 29.5 14. 39.0% 50.9%. Loss on one washing 3 64 Flame tests:

Unwashed-Burning time.

Char length Washed-Burning time V Char length Character of char Inladdition to the above described procedure we have found that a highly satisfactory flameproofing bath may be prepared by an emulsion polymerization procedure. Under this procedure the dialkenyl beta, cyanoethanephosphonate is dispersed in a dilute aqueous solution of polyvinyl alcohol, heated to about 7580 C. and a polymerization catalyst added slowly while stirring. The emulsion, with continuous stirring, is maintained at a temperature of about 80 C. for 2 to 20 hours to effect the desired degree of polymerization. The emulsion thus produced is cooled and employed directly as a fabric treatingbath. Fabrics or fibers treated with such emulsiensare dried, cured and tested for fiameproofness in accordance with the procedures outlined above.

In an example using the emulsion procedure 53.65 grams of diallyl beta, cyanoethanephosphonate were placed in a liter flask equipped with stirrer, thermometer and dropping funnel. While rapidly stirring 92.5 ml. of a 2% aqueous solution of polyvinyl alcohol was added, producing an emulsion. The emulsion was buffered by the addition of 5 grams sodium bicarbonate and solution of 2.15 grams potassium persulfate in 92.5 ml. water added slowly after the temperature of the emulsion had been raised to about 76-78 C. The mixture was held at this temperature for about three hours while completing the polymerization. The emulsion thus produced was cooled to room temperature and used for flameproofing a cotton muslin cloth. V

The cloth was treated with the emulsion, wrung out, dried and cured one hour at 98 C. The add-on" or gain in weight of the cloth was 20.4%. In flameproofing tests the char length was 4%" and the burning time was 7 seconds with the treated but unwashed fabric.

In another example 58 grams of the diallyl beta, cyanoethanephosphonate were emulsified with 92.5 ml. of a 2%. aqueous solution of polyvinyl alcohol and 2.5 grams of a nonionic surface active agent. The emulsion was buffered with 5 grams sodium bicarbonate. 92.5 ml. of water and 1.74 grams of potassium persulfate were then added and the temperature maintained at about 76-81 C. for 2% hours to elfect polymerization of the phosphonate. The resulting emulsion was then used to flameproof an army twill fabric. The cloth was dipped in the emulsion, wrung out, dried and cured 14 minutes at about 140 'C. and retreated a second time in the same.

and a char length of 6% inches and a burning time of 9.8 seconds after washing.

Nomonic surface active agents ma be included in the tion of the fabric. A suitable group of nonionic surface active agents are the reaction products of olefine oxides with lauryl acid ortho and pyrophosphates.

We do not fully understand the theory or mechanism of attaching the above solution and emulsion polymers to the fibers in producing the permanent flameproofing effect, but believe the fibers are coated with the substantially polymerized phosphonate ester and upon curing, further polymerization of the prepolymer or retained traces of monomeirc components firmly attaches the polymer to the fiber. Stiffness in the fabric is Probably avoided by the prepolymerization of the ester before treating the fabric in order to limit the amount of polymerization taking place in the curing step, and thereby substantially limiting the cross welding of one fiber to another in the fabric.

In the solution polymerization procedure the degree of prepolymerization is controlled by regulating the change in viscosity of the solution. If desired, any remaining unsaturation in the prepolymer may be reduced by the addition of bromine. This modification of the procedure may be employed to further control the amount of polymerization which may take place in the final curing of thetrea'ted fabric.

In a typical example using the modified bromination procedure 50 grams of diallyl beta, cyanoethanephosphonate was dissolved in 50 grams B,B'-dichloroethyl ether and polymerized in the presence of 3%' benzoyl peroxide at C. to a viscosity change of 4 times. The partial polymer was then precipitated in 500 ml. of ethyl acetate and washed with an additional 250 ml. of ethyl.

5.5 ml. of triethylamine and concentrated to 25% strengthv under vacuum to produce the final treating bath. A strip of army twill cloth was submerged in the solution for 5.

minutes, wrung out, dried and cured at C. The treated cloth showed a 21% add-on (increase in weight). cloth retained 41% of the treating composition. Flame resistance tests on the unwashed fabric showed a char length of 5% inches anda burning time of 8 seconds:

After washing the flame test showed a char length 'o'f'4.%

inches and a; burning time of -9'seconds, thus, indicating.

a satisfactory permanent 3 flameproofing' effect.

The term fadd-on as used in the above examples means the amount of polymer attached on the fabric and is ex'press'edas percentage by weight of the untreated After washing in a' 0.5% soap solution the fabric. The percentage of add-on will vary with the strength of the impregnating solution, the method removing the excess solution .from the impregnated fabric, and the number of impregnation treatments. For satisfactory results the amount of add-on should be at least 10%, but generally we prefer to use from 15% to 40%. However, as little as add-on will give an appreciable flameproofing etfect.

The solution polymerization and flameproofing procedure, as well as the procedure using bromination, are described and claimed in the copending application of A. D. F. Toy, R. S. Cooper and T. P. Traise, Serial No. 381,761, filed September 22, 1953.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary 1imi tations should be understood therefrom as modifications will be obvious to those skilled in the art.

We claim:

1. The method of flameproofing cellulosic fibers which comprises impregnating the fibers with an aqueous emulsion of a partial polymer of a beta, gamma, unsaturated dialkenyl beta, cyanoethanephosphonate wherein each alkenyl group is a member of the class consisting of allyl and methallyl radicals, substantially drying the fibers and heating the fibers at a polymerizing temperature and for a time sutficient to effect further polymerization and attachment of the resulting polymer to the fibers.

2. The method of preparing a flameproofing emulsion which comprises suspending a beta, gamma, unsaturated dialkenyl beta, cyanoethanephosphonate wherein each alkenyl group is a member of the class consisting of allyl and methallyl radicals, in a dilute aqueous solution of polyvinyl alcohol, adding a polymerization catalyst and heating the emulsion for a sufiicient period to effect partial polymerization of the phosphonate ester therein.

3. The method of claim 2 wherein each alkenyl group is an allyl radical.

4. The method of claim 2 wherein each alkenyl group is a methallyl radical.

5. The method of claim 1 wherein the polymer coating is present in an amount between about 5-40% by weight of the fibers.

6. The method of claim 2 wherein the catalyst is potassium persulfate.

7. A fiber treating composition comprising; an emulsion of a substantially polymerized beta, gamma, unsaturated dialkenyl beta, cyanoethanephosphonate wherein each alkenyl group is a member of the class consisting of allyl and methallyl radicals, in a dilute aqueous solution of polyvinyl alcohol.

8. The method set forth in claim 2 wherein the emulsion is heated to at least about C. for about 2-20 hours.

References Cited in the file of this patent UNITED STATES PATENTS 1,581,779 Brandt Apr. 20, 1926 2,660,542 Walter et al. Nov. 24, 1953 2,660,543 Walter et al. Nov. 24, 1953 2,681,920 Van Winkle June 24, 1954 2,686,768 Frick et a1 Aug. 17, 1954 2,714,100 Fon Toy et a1 July 26, 1955 2,725,311 Kenega et al Nov. 29, 1955 2,780,616 Dicket et al. Feb. 5, 1957 UNITED STATES PATENT OFFICE CERTIFICATE 0F 'CQRRECTION Patent No 2341 507 July 1, 1958 James a, Costello, Jr., et e10 It is hereby certified that error appears in the-printed specificatior of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below,

(3011111111 2, line 3, for "satisfactoy" read W satisfactory columns 3 and 4, in the Table, heading to first column thereof, for limperiment N0 read me Experiment No e column 4, line 32, for

"monomeirc" read monomeric e Signed and sealed this 25th day of November 1958o (SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents 

1. THE METHOD OF FLAMEPROOFING CELLULOSIC FIBERS WHICH COMPRISES IMPREGNATING THE FIBERS WITH AN AQUEOUS EMULSION OF A PARTIAL POLYMER OF A BETA, GRAMMA, UNSTAURATED DIALKENYL BETA, CYANOETHYANEPHOSPHONATE WHEREIN EACH ALKENYL GROUP IS A MEMBER OF THE CLASS CONSISTING OF ALLYL AND METHALLYL RADICALS, SUBSTANTIALLY DRYING THE FIBERS AND HEATING THE FIBERS AT A POLYMERIZING TEMPERATURE AND FOR A TIME SUFFICIENT TO EFFECT FUTHER POLYMERIZATION AND ATTACHMENT OF THE RESULTING POLYMER TO THE FIBERS. 